Chremistica umbrosa can be found in South-East Asia, in particular Singapore. If you go to see them, bring an umbrella. I don’t know why these cicadas pee this often, but I imagine they are eliminating some toxin or waste or chemical (sugar, perhaps) that is not good for them.
Watch the videos:
They piddle out water from their sap meal. The meal is calorie poor, so you have to imbibe a great deal and get rid of the excess! Think of it as “light beer”!
Indeed, an umbrella seems necessary! Cicadas can probably sap up to hundreds times their body weight each day, as the other xylem sap-feeders. And the fact that this species is gregarious perhaps explains that we can see such a rain. But this video is still very impressive.